This invention relates to a method of overlaying or more specifically diffusion cladding a Fe-containing metallic base material for decorative articles and ornaments with an alloy of Au, Pt, and/or Pd bases.
The present inventor has invented a method of the above-mentioned kind, and obtained U.S. Pat. No. 4,309,461 of Jan. 5, 1982, in which there is described a method of overlaying an austenite stainless steel material for decorative articles and ornaments with an alloy of Au, Pt, and/or Pd bases, which comprises plating selected surfaces of the steel material with the constituents of said alloy in any desired order, and one at a time in a plurality of successive layers, and with each layer being of a thickness and volume which corresponds to the constituent ratios of the alloy of a desired purity and dimension, and heating the layers to a temperature sufficient to cause them to liquid phase alloy.
It is now found by him that the alloy of Au, Pt, and/or Pd bases which is overlaid on an ingot stainless steel material for fabricating decorative articles and ornaments such as spectacle frames, watch casings, and watch bracelets by the aforementioned method, does not sometimes have hermetically sealed bonds with the steel material. And, boundaries between the alloy and the steel material sometimes discolor on account of sweat which passes into the boundaries. Sometimes, the alloy comes off partly from the base material. This is because that when an alloy of the aforementioned kind is heated, its diffusion into the stainless steel occurs, while constituents of stainless steel such as Fe, Cr, Ni and others, and particularly Fe which are activated by Au, Pd and/or Pt under an elevated temperature come up into the alloy, too. This Fe which diffuses into the alloy, forms metallurgically emulsion with Ag in the alloy, which emulsion gives, when it is cooled, fissility to the interfacial boundaries between the base steel material and the precious metal alloy cladded onto said base.